Around 15 million Iraqis have the chance to vote today in a landmark provincial election that will test the nation's fragile stability and measure the popularity of Prime Minister Nuri al-Maliki.

Around 15 million Iraqis have the chance to vote on Saturday in a landmark provincial election that will test the nation's fragile stability and measure the popularity of Prime Minister Nuri al-Maliki.

Iraq's 800,000-strong police and military have been deployed in strength across the country as part of ramped-up measures aimed at preventing attacks by Al-Qaeda and other insurgents.

Authorities have sealed Iraq's borders, shut down airports and imposed transport bans and night-time curfews as part of the massive security lockdown ahead of the 7 am (0400GMT) opening of the polls on Saturday.

The steps follow the shooting dead of five election contenders and workers in Baghdad and in the cities of Mindali and Mosul, north of the capital, on Thursday night, raising security fears.

The ballot being held in 14 of 18 Iraqi provinces will be a crucial test of the country's stability, especially as US combat troops accelerate plans to leave the country and beat the agreed exit deadline of the end of 2011.

US President Barack Obama, who as a candidate urged a 16-month timetable for withdrawal of the troops, sees the elections as a "significant milestone" in Iraq's fledgling democracy, White House spokesman Robert Gibbs said on Friday.

"Obviously the president will watch the results, and believes that the provincial elections this weekend mark another significant milestone in Iraq's democratic development," Gibbs said.

Sunni Arabs are expected to turn out in large numbers in a reversal of the January 2005 parliamentary elections they boycotted. The vote is also being seen as a quasi referendum on the leadership of Maliki.

The Shiite premier has emerged in recent months as stronger-than-expected leader, promoting a secular national agenda in response to the sectarian strife that tore Iraq apart in the wake of the 2003 US-led invasion.

Although Maliki is not standing in the election, he has thrown his support behind a list of candidates that make up the State of Law Coalition.

Pundits say Maliki's list could do well because in March last year, he ordered security forces to take on militiamen loyal to firebrand cleric Moqtada al-Sadr in his strongholds of Basra and Baghdad.

The victory over Sadr has raised Maliki's stature among Iraqis sick of sectarianism, and even sparked a debate over secular and religious politics.

In the run-up to the elections, Shiite clerics have urged Iraqis to vote.

"We appeal to the people; Sunnis, Shiites, Arabs, Kurds and Turkmen to participate in the elections," prayer leader Sadr al-Din al-Qubanchi said in the holy Shiite city of Najaf.

"You must vote to express the will of the people and not to repeat the mistake made in the 1920s when (Shiites) refusal to participate led Iraq to a dictatorship and bloodshed."

He was referring to the time when Shiite religious leaders forbade followers to take part in the structure of the newly formed Iraqi state that was under British occupation.

Still angry in 2005 about the US-led invasion to depose Sunni dictator Saddam Hussein, followers of that faith boycotted the nation's first democratic elections, a move that left them under-represented in the government.

Yemen-based Sheikh Abdel Karim Zeidane, a Sunni and founder of the Muslim Brotherhood of Iraq, rejected the notion that Saturday's poll would legitimise the occupation.

"To say that we will not vote because it legitimised the occupation is ridiculous," he said in a pamphlet distributed in the Sunni areas of Baghdad.

More than 14,400 candidates are competing for 440 seats in provincial councils, which appoint the governor and oversee finance and reconstruction, with a combined budget of 2.5 billion dollars.

The vote will not include the three autonomous Kurdish provinces -- Arbil, Dohuk and Sulaimaniyah, all in the north.

Elections have been postponed in the oil-rich Kirkuk province, which the Kurds want to incorporate despite fierce opposition by the central government.